Ser/thr phosphatases dephosphorylate their targets with high specificity, yet the structural and sequence determinants of phosphosite recognition are poorly understood. Calcineurin (CN) is a conserved Ca/calmodulin-dependent ser/thr phosphatase and the target of immunosuppressants, FK506 and cyclosporin A (CSA). To investigate CN substrate recognition we used X-ray crystallography, biochemistry, modeling, and in vivo experiments to study A238L, a viral protein inhibitor of CN. We show that A238L competitively inhibits CN by occupying a critical substrate recognition site, while leaving the catalytic center fully accessible. Critically, the 1.7 Å structure of the A238L-CN complex reveals how CN recognizes residues in A238L that are analogous to a substrate motif, “LxVP.” The structure enabled modeling of a peptide substrate bound to CN, which predicts substrate interactions beyond the catalytic center. Finally, this study establishes that “LxVP” sequences and immunosuppressants bind to the identical site on CN. Thus, FK506, CSA, and A238L all prevent “LxVP”-mediated substrate recognition by CN, highlighting the importance of this interaction for substrate dephosphorylation. Collectively, this work presents the first integrated structural model for substrate selection and dephosphorylation by CN and lays the groundwork for structure-based development of new CN inhibitors.
Idiopathic focal segmental glomerulosclerosis (FSGS) is among the most common, morbid and treatment-resistant conditions faced by nephrologists. While glucocorticoids have traditionally been the mainstay of initial treatment, they induce remission in only a minority of patients. A variety of other immunosuppressants have been utilized against steroid-resistant FSGS, but few have been rigorously examined in well-controlled trials. Recently, the results were published from a National Institutes of Health (NIH)-sponsored multicenter randomized trial comparing cyclosporine (CSA) with a combination of mycophenolate mofetil (MMF) and pulse dexamethasone (DEX) for the treatment of steroid-resistant FSGS. No difference in treatment effectiveness was shown between the two groups, and adverse effects were comparable. This was the largest randomized trial ever undertaken in FSGS, but it was unfortunately underpowered to show clinically relevant differences in response rates. This shortcoming, along with particularities of the study population and outcome measures, makes it challenging to draw definitive conclusions from the trial results. Despite these limitations, the trial does provide valuable insights into treatment strategies for FSGS and offers important lessons for planning future research.
: The influence of the conversion from cyclosporine (CsA) to everolimus (EVR) on the chronopharmacokinetics of mycophenolic acid (MPA) and its glucuronide (MPAG) and acyl glucuronide (acyl-MPAG) metabolites in patients receiving enteric-coated mycophenolate sodium (EC-MPS) has not been studied.
The objective of this study was to compare efficacy and safety of alemtuzumab, antithymocyte globulin (ATG), and daclizumab for induction therapy in organ transplantation.
Every month, new releases on the relationship between pharmacogenetic biomarkers and immunosuppressive drug therapy in kidney transplantation are published. However, the systematic clinical application of these discoveries occurs at a very slow pace, and the usefulness of knowing a patient’s genotype remains an important matter of debate. This can be partially ascribed to the lack of consistency when looking at the different associations reported across several studies but also the need for a broad-spectrum view and a rigorous analysis of the relevance of the different associations observed to date. For that purpose, we performed a comprehensive analysis of the strength of the different reported genetic associations, and in this article we discuss their potential for clinical implementation in kidney transplantation. For tacrolimus, it is likely that a genotype-based drug dosage can benefit patient outcome, while for ciclosporin A, the data appear less convincing. For the mammalian target of rapamycin inhibitors, sirolimus and everolimus - given the lack of data and the absence of large prospective studies - it is premature to implement pharmacogenetics, but some novel and promising leads have recently been reported. For mycophenolate mofetil, the complex metabolic pathways of its active moiety, mycophenolic acid, complicate analysis of the various published associations. However, at present, some interesting findings can be highlighted and offer potential value to assist clinicians in decision making.
The time necessary for a treatment to become effective is crucial for patients and physicians but has been largely neglected in the reporting and comparison of clinical trials in dermatology. The aim of this systematic review is to determine the time until the onset of action of systemic agents approved for moderate-to-severe psoriasis. Primary outcome is the time until onset of action (TOA) defined as the weighted mean time until 25% of the patients achieved a PASI 75 response. Among the biologics, infliximab has the shortest TOA (3.5 weeks) followed by ustekinumab (high dose 4.6/low dose 5.1 weeks/not weight adapted), adalimumab (4.6 weeks), etanercept (high dose 6.6/low dose 9.5 weeks) and alefacept (high dose 15.4 weeks/ low dose: no data). Among the conventional treatments, good data is available for CsA (TOA: 6.0 weeks), limited data was found for MTX (TOA: high dose 3.2/low dose 9.9 weeks). No data are available for fumaric acid esters and retinoids. This systematic review provides clinically relevant information on the onset of action of antipsoriatic agents although the data currently available allows only a limited assessment. Psoriasis trials should consider including the time until the onset of action as an additional outcome measure.Journal of Investigative Dermatology accepted article preview online, 20 February 2013; doi:10.1038/jid.2013.78.
The efficacy of rituximab (RTX) as the sole therapy for preventing relapses of nephrotic syndrome (NS) is transient in most patients; therefore, the optimal therapy required for maintaining a successful response to a biological agent remains a challenge. We conducted a prospective study to compare the efficacy of cyclosporine (CsA) with that of mycophenolate mofetil (MMF) as maintenance therapy after a single infusion of RTX. Of 29 patients with persistent steroid-dependent NS despite the use of CsA and/or MMF, 13 without chronic nephrotoxicity continued CsA therapy, maintaining a 2-h post-dose CsA level of 400-500 ng/ml (CsA group). The remaining 16 were treated with MMF, maintaining a pre-dose level of 2-5 μg/ml of mycophenolic acid (MMF group). The median duration of CsA and MMF treatment was 18 and 19 months, respectively. Despite the mean number of relapses before RTX treatment being significantly lower in the MMF group than in the CsA group (2.3/year vs. 4.6/year, p < 0.01), treatment failure occurred more frequently in the MMF group (7/16) than in the CsA group (2/13). The rate of sustained remission was also significantly higher in the CsA group than in the MMF group (p < 0.05). Conclusion: In patients with severe steroid-dependent NS, CsA appears to be more effective than MMF for maintaining remission after a single infusion of RTX.
A European League Against Rheumatism (EULAR) task force was established to define points to consider on use of antirheumatic drugs before pregnancy, and during pregnancy and lactation. Based on a systematic literature review and pregnancy exposure data from several registries, statements on the compatibility of antirheumatic drugs during pregnancy and lactation were developed. The level of agreement among experts in regard to statements and propositions of use in clinical practice was established by Delphi voting. The task force defined 4 overarching principles and 11 points to consider for use of antirheumatic drugs during pregnancy and lactation. Compatibility with pregnancy and lactation was found for antimalarials, sulfasalazine, azathioprine, ciclosporin, tacrolimus, colchicine, intravenous immunoglobulin and glucocorticoids. Methotrexate, mycophenolate mofetil and cyclophosphamide require discontinuation before conception due to proven teratogenicity. Insufficient documentation in regard to fetal safety implies the discontinuation of leflunomide, tofacitinib as well as abatacept, rituximab, belimumab, tocilizumab, ustekinumab and anakinra before a planned pregnancy. Among biologics tumour necrosis factor inhibitors are best studied and appear reasonably safe with first and second trimester use. Restrictions in use apply for the few proven teratogenic drugs and the large proportion of medications for which insufficient safety data for the fetus/child are available. Effective drug treatment of active inflammatory rheumatic disease is possible with reasonable safety for the fetus/child during pregnancy and lactation. The dissemination of the data to health professionals and patients as well as their implementation into clinical practice may help to improve the management of pregnant and lactating patients with rheumatic disease.
To report the 10-year follow-up of the MAINTAIN Nephritis Trial comparing azathioprine (AZA) and mycophenolate mofetil (MMF) as maintenance therapy of proliferative lupus nephritis, and to test different definitions of early response as predictors of long-term renal outcome.
Immunosuppressive drugs are used in the treatment of inflammatory and autoimmune diseases, as well as in transplantation. Frequently prescribed in young people, these treatments may have deleterious effects on fertility, pregnancy outcomes and the unborn child. This review aims to summarize the main gonadal side effects of immunosuppressants, to detail the effects on fertility and pregnancy of each class of drug, and to provide recommendations on the management of patients who are seen prior to starting or who are already receiving immunosuppressive treatment, allowing them in due course to bear children. The recommendations for use are established with a rather low level of proof, which needs to be taken into account in the patient management. Methotrexate, mycophenolate, and le- and teri-flunomide, cyclophosphamide, mitoxanthrone are contraindicated if pregnancy is desired due to their teratogenic effects, as well as gonadotoxic effects in the case of cyclophosphamide. Anti-TNF-alpha and mTOR-inhibitors are to be used cautiously if pregnancy is desired, since experience using these drugs is still relatively scarce. Azathioprine, glucocorticoids, mesalazine, anticalcineurins such as cyclosporine and tacrolimus, ß-interferon, glatiramer-acetate and chloroquine can be used during pregnancy, bearing in mind however that side effects may still occur. Experience is limited concerning natalizumab, fingolimod, dimethyl-fumarate and induction treatments.